Phosphor devices are used in lighting apparatus wherein the phosphor (component or mixture), i.e. a substance with wavelength-converting properties, e.g. a fluorescent or luminescent substance, is remote from the exciting light source. Therefore, they are also called remote phosphor devices. Remote phosphor devices can be used in various lighting applications, e.g. in RGB projection equipment, generating red (R), green (G) and blue (B) light for coloured video projection. Other possible lighting applications comprise medical, architectural or entertainment lighting with coloured or white light.
In prior art remote phosphor devices, such as phosphor wheels, the phosphor is coated on a carrier plate. The phosphor is excited by exciting light, e.g. visible blue laser light (450 nm), impinging on the phosphor layer. The exciting laser light is wavelength-converted by the phosphor to generate light with longer wavelengths (e.g. broad spectral distribution with a peak at approximately 520 nm for green light).
The wavelength-converted light from the phosphor is collected by an optical transmitting member, e.g. an optical collimator such as a lens made of glass, arranged in front of the phosphor.